Ocean Deposits

Ocean deposits are the unconsolidated sediments (Inorganic or Organic ) derived from various sources deposited on the oceanic floor.

What are the sources of these ocean deposits ?

These ocean deposits are derived from three major sources:

1- Terrigenous Sources

2- Volcanic Deposits

3- Pelagic Deposits

What are Terrigenous Deposits ?

Weathering is an ongoing process being carried upon,on the various continental rocks by numerous mechanical and chemical agents. As a result of which, these rocks get disintegrated and get decomposed to form fine to coarse sediments.These sediments brought by rivers, streams, winds, glaciers, oceanic currents, waves etc get deposited upon the continental margins are thereby known as terrigenous deposits.

The shape and size of these materials differ which in turn influence their seaward distribution. Bigger sized sediments get deposited near the coast such as boulders, cobbles and pebbles, while the finer sediments get deposited away from the sea coast.

On the basis of size of particles and density, following pattern has been identified.

Deposit

Size( Diameter)

Gravel

2mm- 256mm

Sand

1mm – 1/16mm

Silt

1/32mm – 1/256mm

Clay

1/256mm – 1/8192mm

Mud

Finer than 1/8192mm

ocean deposits

Mud has been further classified into following categories:

Type of Mud

Characteristics

Blue Mud

Sediments derived from rocks containing Iron Sulphide and decomposed organic content.

Red Mud

Sediments derived from rocks containing Iron Oxide

Green Mud

Color of blue mud changes into green due to reaction with sea water. It Contains silicates of potassium and glauconites

Coral Mud

Derived from coral reefs located on continental shelf

 What are Volcanic Deposits  ?

These are the materials which are deposited in marine environment by volcanic eruptions on land which are carried by wind, river, rain wash etc to the oceans and volcanic eruption in the ocean which deposit sediments directly into the ocean.

What are Pelagic Deposits ?

These are the organic and Inorganic sediments deposited on the ocean floor. They are derived from the skeletons of marine organisms and marine plant remains.

They can be categorized into :

Organic Material

Characteristics

Neretic Matter

Contain skeletons of marine organisms and plant remains. These include shells of

molluscs, skeletons of radiolarians and spicules of sponges, calcareous and siliceous plant remains.

Pelagic Matter

It consists of matter derived from algae and they are generally referred to as ooze.

On the basis of relative content of calcium carbonate or silica, pelagic deposits can be divided into :

1- Calcareous ooze

2- Siliceous ooze

Calcareous ooze

Pteropod

Globigerina

Derived from bio- decomposition of mollusc skeletons. Derived from bio- decomposition of zooplanktons.
Mollusc is marine invertebrate. Globigerina are marine protozoans.
These deposits are more prevalent in Atlantic and Indian Ocean These deposits are most extensive in pacific ocean.

 

Siliceous Ooze

Diatom

Radiolarian

Derived from bio- decomposition of marine phytoplankton. Derived from bio- decomposition of radiolaria
Phytoplankton are marine microscopic algae. Radiolarians are marine protozoans
They are most extensive in Pacific Ocean. They are most extensive in Pacific Ocean.

Volcanic dust deposited on the oceanic floor are the source of Inorganic Pelagic deposits. They are also called as Red Clay as it is rich in iron oxide.

 

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